1. Technical Field
The present invention relates to a recording medium recording a program for a method of data management and a method of image creation, a transmission medium transmitting a program for a method of image creation, a recording medium recording a program for a method of image restoration, and a transmission medium transmitting a programs for a method of image restoration, and more particularly relates to a method of data management for distributing digital content with annex information visibly arranged, a recording medium recording a program for a method of image creation for using distributed image data in the method of data management, a transmission medium for transmitting the program, a recording medium recording a program for a method of image restoration for using distributed image data, and a transmission medium transmitting the program.
2. Description of Related Art
For software such as computer programs and electronic publications, computerized data are stored on magneto-optic disks (MO), DVD, floppy disks (FD), mini discs (MD), etc., and sold. These computerized data are easily duplicated, and illegal duplicates are frequently made. On this account, software vendors' and publishers' copyrights are notably encroached and profits notably hindered.
Computerized data including static images and moving images distributed via the Internet, CATV, etc. are also illegally duplicated, which spoils copyright holders' profits.
To protect computerized data referred to as “digital content” stored on recording media or distributed via a network, the digital content is encrypted using an encryption key, and the encrypted substantive data are distributed.
For example, consider that a user accesses a distributor of content from his/her personal computer and downloads digital content to the hard disk to use. Firstly, the user accesses a host computer to obtain a plug-in module for downloading. After that, an identification number of a hard disk drive being used, a CPU identification number of the computer being used, and other use-specific identification information are sent to the host computer.
On the content distributor end substantive data, in which digital content has been encrypted with a content key, and licensing data, in which the content key has been encrypted with user-specific identifying information, are sent to the user end.
The user stores the encrypted substantive data and the authorization information which are left encrypted on the hard disk. When the user uses the digital content, the user decrypts the authorization information using the identification information such as an identification number of the hard disk drive and obtains the content key. With the content key, the user decrypts the encrypted digital content to use.
In this case, an encryption key for coding digital content can be made to be common when right of digital content availability is granted to individual users, and the right of availability can be individually granted by coding a decryption key by using a user-specific information which differs depending on the user.
When data are distributed in the above manner, a data distributor needs to individually send encrypted digital content and authorization information which is a decryption key of encrypted digital content.
Meanwhile users need to individually store the encrypted digital content sent that has been sent in and their authorization information on a recording medium.
Therefore if authorization information is destroyed while it is being sent from a data distributor to a user, or is destroyed or lost on a user's recording media due to some accident, digital content cannot be used and a procedure for obtaining the authorization information must be performed again.
Further, in situations in which library apographs and art museum collections are by photographing or scanning imported as image data that is used by users, if the image data is completely encrypted, pinpointing the image data desired on the users' end before transacting authorization information is difficult.
Therefore it is desirable that part of the image can be checked by users and the image cannot be illegally diverted.
For this reason, it is conceivable that annex information such as copyright information is embedded in digital content and distributed as a visible digital watermark as shown in Japanese Laid-Open Pat. App. 1996-241403.
When annex information is embedded in digital content and distributed as a visible digital watermark, modulation data of color or brightness must be created for each pixel and be distributed with digital content with annex information to eliminate the annex information and restore the original digital content. Therefore there occur problems that transmission and receive of such data is time-consuming and large memory capacity for storing data is consumed.